USB standard technology was developed as a bus for connection between computers and electronic devices. The USB connection was designed to provide both communication and a power supply. Since its introduction, however, USB has evolved to replace a variety of computer interfaces, such as serial and parallel ports. USB has also evolved for use as a separate power charger for portable devices. With respect to the electrical power related to USB, the USB standard defines an electrical signal of 5 volt DC, with a maximum voltage of 5 V (±5%).
Many consumer products including, for example, I-pads, cell phones, PDA's, etc. (“USB powered devices”), derive their operating/battery recharge power from the (nominal) 5 volt DC power available on a computer USB port. AC wall mount charging adapters, which also utilize the USB connector as the connection point for the power supply, have become popular to recharge these USB powered devices when a computer USB port is not available. Such adapters generally include an AC power plug and a USB port or wire to a USB or other universal connector, such as an Apple dock connector. Of course, when referring to USB connectors, it is understood that there are many different types of USB connectors, including Type A, Type B, Mini-A, Mini-B, Micro-A, Micro-B, Apple dock connectors, etc., all of which are intended to be covered herein.
There are also retail, commercial and other applications requiring the fixed or semi-permanent mounting of USB powered devices. For example, stores often provide tablets such as iPads for an employee to search, provide customer information and/or order from one or more fixed locations in a retail establishment. In such applications, the USB powered devices are typically powered from an AC power adapter, requiring that an AC receptacle be installed at each location at a cost of several hundred dollars.
Similarly, USB “Charging Stations” are provided for convenience in many public areas, such as airports and conference facilities. These charging stations are provided to allow charging of USB powered devices when traveling. Such charging stations are also typically powered from an AC line which requires a receptacle and costly line power connection.
Power over Ethernet, or POE, technology describes a system for passing electrical power safely along with data on Ethernet lines or cables. Power is supplied in common mode over one of two designated differential pairs of wires in the Ethernet cables, originating from a power supply within a POE enabled network. The original IEEE 802.3af-2003 POE standard provided up to 15.4 watts of DC power to each device, however, the updated IEEE 802.3 at-2009 POE standard provides up to 25.5 watts of power. The voltage range available with POE is from about 37 to about 57 volts.
POE technology is considered especially useful for powering certain devices which require more power than USB offers and when longer runs of cable are required than USB permits. In this regard, Category 5 POE cable and power radios and other low power devices through over 100 meters of cable, an order of magnitude farther than the theoretical maximum of USB.
Moreover, POE cable is considered to be easy to run and is readily available in most commercial spaces. Due to the low DC voltage of POE compared to standard AC power supply, the installation of a POE cable drop does not require an electrician. Therefore, bringing low DC voltage POE power to locations fairly remote from a power supply via POE cable has been shown to be cost effective.
Notwithstanding the above, there is a need for providing USB power from remote power supplies over relatively long distances, when considering USB power, in an efficient and cost effective manner.